Low supply

I've had low supply since the begining. My baby is 12 weeks now. (She had trouble latching at the beginning and lost too much weight so the doctor told me I had to supplement and I know both those things probably caused my supply to drop.) Her latch is perfect now and it has been for a while, and I try and nurse as much as possible and not give her formula unless she seems hungry after a feed (usually in the evenings only.) How can I tell if my supply is back up? I've tried so many things to increase it, but when I pump after she eats I get maybe 1oz. I've heard that's not an indicator of your supply , so what is?

Heeeelp! Thank you:)